Radio communication with very short waves



Nov. ,17, 1936.

E. GERHARD 2,060,934

RADIO COMMUNICATION WITH VERY SHORT WAVES Filed March 2'7 1930 /n venfor:

Z erhar/ Patented Nov. 17, 1936 UNITED STATE FATE? OFFICE RADIO COMMUNICATION WITH VERY SHORT WAVES Utrecht, Netherlands Application March 27, 1930, Serial No. 439,467 In Germany April 2, 1929 7 Claims.

' In the arrangements hitherto employed for the production of very short electrical waves, of a length for example of less than 5 metres, a highfrequency modulation of these waves is very difiicult to carry out, since, as is known, any coupling element or portion of a conductor connected to the electrodes of the transmitting valve increases the wave length and also afiects the generating of oscillations in other Ways.

According to the present invention, for generating ultra-short waves modulated at a high frequency, an arrangement is used in which the generating of the ultra-short waves is effected by the Barkhausen and Kurz method, known in itself.

Experiments have shown that with this method of generating oscillations the influencing of the Wave length by connecting the coupling and conducting elements required for high-frequency modulation can easily be prevented. For the generating of ultra-short waves modulated at a high frequency, therefore, the employment of the above-mentioned method, in combination with a modulating arrangement, such as is described below, presents special advantages.

The invention is diagrammatically illustrated by way of example in Figure 1 to 7 of the accompanying drawing, each of which represents a circuit diagram.

In Figure 1, 2 denotes a thermionic valve having a filament, a grid 4 and a braking electrode 3. To the grid 4 is applied a high positive voltage of some hundreds of volts, and to the braking electrode 3 a smaller negative voltage, which may be obtained for example from a potentiometer 6. With a particular adjustment of the operative data, ultra-high-frequency thermionic oscillations occur in the valve, the frequency ii of which is primarily dependent upon the working voltages applied. According to the type of valve employed, the frequency f1 also depends upon a small oscillating circuit introduced into the valve, or upon a Lecher system connected to the electrodes of the valve. On the other hand the frequency f1 of the ultra-high-frequency oscillations generated by the valve in this way is completely independent of the length and arrangements of the leads, and also of the oscillating circuits included in the leads, for instance the oscillating circuit III, II in Figure 1. I assume that the thermionic valve I'I generates, with the known back-coupling connection, any desired high-frequency f2, which is lower than the ultra-high frequency f1 generated by the valve 2. For the purpose of generating the high-frequency h, the coil I6 is now coupled to the oscillating circuit I2, I5 and is also coupled to the coil II of the oscillating circuit III, II. In this way there arises between the braking electrode 3 and the filament or the grid 4 a high-frequency alternating voltage of the frequency ,fz, as a result of which the ultrahigh-frequency oscillations generated by the valve 2 are modulated with the frequency f2. The ultra-short waves modulated at a high frequency are radiated either by the system located in the interior of the valve or by a bi-pole I coupled thereto. The idea of the invention is not altered if instead of the high-frequency generator I2, I5, I6, II, shown in Figure 1, any other desired highfrequency generator is employed. On the other hand it is characteristic of the invention that the exciting of oscillations in the valve 2 is effected in the braking field connection described.

The generating of the high-frequency oscillations f2 employed for modulation may be effected according to the present invention by the same valve by which the ultra-high frequency oscillations f1 are generated.

It has been found that thermionic valves which are connected in the braking field connection, and. which oscillate at an ultra-high frequency, have a drooping current-voltage characteristic in the oscillating condition. If for example, as shown in Figure 1, between the electrode 3 and the oathode, any desired high-frequency or low-frequency oscillating circuit Ill, II is connected, in which case the oscillator I2, I5, I5, II will not however be present, this oscillating circuit excites itself at its natural frequency f2, quite independently of the frequency f1 of the ultra-high-frequency oscillations primarily generated by the valve 2. By this means the ultra-high-frequency oscillations h are modulated at a high or low frequency according to the magnitude of the frequency f2. The high-frequency or low-frequency oscillations f2 generated in this way in the oscillating circuit III, II may of course be employed not only for the modulation of the ultra-short waves generated at the same time by the valve 2 but also in other ways; for instance they may serve in their turn as a transmission wave.

In Figure 2 an oscillating circuit 29. 3!) cor responding to the oscillating circuit III. II is connected between the electrode 3 and the grid 4 of the thermionic valve 2. The high positive voltage G is supplied to the grid by a choking coil 21. The voltage for the electrode 3 is applied at P. The frequency generated in the circuit 29-30 and modulating the Barkhausen-Kurz high frequency may be partially taken from the circuit car by the coil 3| for any other purposes and transmitted to another utilization circuit. Consequently, these oscillations may be used several times if desired.

In Figure 3 the circuit 29, 30 oscillating at the frequency f2 is located between the grid and the cathode of the valve 2. For the rest, what has been stated for Figures 1 and 2 applies here also.

In Figure 4 the oscillating circuit consisting of the coil 38 and the condenser 29 is located between an auxiliary grid and the cathode. The method of operation of this arrangement again corresponds to that of the circuits shown in Figures l to 3.

An increase in the oscillation output and in the stability of the high frequency f2 secondarily generated by the valve 2 is obtained according to the present invention by coupling together two or more oscillating circuits located between each two electrodes of the valve connected in the braking field connection.

Figure 5 shows a useful arrangement for this purpose. To the grid 4 of the valve 2 is applied a high positive voltage G, and to the electrode 3 a lower positive or negative voltage P. In the valve 2, ultra-high-frequency oscillations of the frequency h are generated. With a suitable selection of the voltages G and P, there also arise in the oscillating circuit I0, I I, and independently thereof in the oscillating circuit 24, 25, highfrequency oscillations of the frequency f2. The oscillating circuits II], II and 24, 25 are tuned to the same frequency and coupled to one another.

Figure 6 shows an arrangement by which the Ultra-high-frequency oscillations of the frequency f1 generated by the valve 2 can be'modulated both with the high frequency f2 determined by theoscillating circuit I0, II and at a low frequency. Part of the coil I I forms the secondary winding or a modulating choke, upon the core 2| of which, besides the winding I I, there is a winding 22, which is connected with a low-frequency amplifier.

Figure 7 shows an arrangement in which the oscillating circuit I0, II is excited at a high frequency, and the oscillating circuit 24, 25 at a low frequency, the self-excitationof these circuits beingagain effected in the same manner as has been described above. With this arrangement a simultaneous high-frequency and low-frequency modulation of the ultra-short waves generated by the valve 2 is likewise obtained.

Speaking generally, according to the present invention, a high-frequency and low-frequency modulation of the ultra-short transmission waves is effected owing to the fact that the highfrequency by which the ultra-short Waves are modulated in one of the arrangements hereinbefore described is in its turn modulated as a low frequency by known means.

What I claim is:-

1. An arrangement for generating ultra-short electrical waves modulated at a high frequency, comprising a thermionic valve having a filament and consisting of a grid electrode of high positive voltage of several hundred volts and a braking electrode of a lower voltage of only a few volts in relation to the filament, producing ultra-high-frequency thermionic oscillations in the valve and means for applying between two electrodes of the valve a supplementary highfrequency alternating voltage, said last mentioned means including a high-frequency, parallel' tuned. oscillating circuit, connected between two electrodes of the thermionic valve, and a high frequency generator coupled to said oscillating circuit.

2. An arrangement for generating ultra-short electrical waves modulated at a high frequency, comprising a thermionic valve having a filament and consisting of a grid electrode of high positive voltage of several hundred volts and a braking electrode of a lower voltage of only a few volts inrelation to the filament, producing ultra-high frequency thermionic oscillations in the valve and means for applying between twoelectrodes of the valve a supplementary high-frequency alternating voltage, the last mentioned means including an oscillating circuit connected between two electrodes of the valve, the natural frequency of said circuit being essentially diiferent from the frequency of the ultra-short waves primarilyl generated by the valve, whereby secondary electrical oscillations arise in this oscillating circuit.

' 3.-An arrangement for generating ultra-short electrical waves modulated at a high frequency, comprising a thermionic valve having a filament and consisting of a grid electrode of high positive voltage of several hundred volts and a braking electrode of a lower voltage of only a few volts in relation to the filament, producing ultrahigh-frequency thermionic oscillations in the valve and means for applying betweentwo electrodes of the valve a supplementary high-frequency-alternating voltage, said last mentioned means including two oscillating circuits coupled together, each being connected between two elec trodes of the valve.

4. An arrangement for generating ultra-short electrical waves modulated at a high frequency, comprising a thermionic valve having a filament and consisting of a grid electrode of high positive voltage of several hundred volts and a braking electrode of a: lower voltage of only a few volts in relation to the filament, producing ultrahigh-frequency thermionic oscillations in the valve and means for applying between two electrodes of thevalve a supplementary high-frequency alternating voltage, said last mentioned means including a high-frequency parallel tuned oscillating circuit, connected between grid and cathode of the thermionic valve, and a highfrequency generator coupled to said oscillating circuit.

5. An arrangement for generating ultra-short electrical waves modulatedat a high frequency, comprising a thermionic valve having a filament and consisting of a grid electrode of high positive voltage of several hundred volts and a braking-electrode of a lower voltage of only a few volts in relation to the filament, producing ultrahigh-frequency thermionic oscillations in the valve and means for applying between two electrodes of the valve a supplementary high-frequency alternating voltage, said last mentioned means including an oscillating circuit connected between braking electrode and cathode of the valve, the natural frequency of said circuit being essentially different from the frequency of the ultra-short waves primarily generated by the valve, whereby secondary electrical oscillations arise in this oscillating circuit.

6.-An' arrangement for generating ultra-short electrical waves modulated at. a high frequency,

comprising a thermionic valve having a filament and consisting of a grid electrode of high positive voltage of several hundred volts and a braking electrode of a lower voltageof only a few Volts in relation to the filament, producing ultrahigh-frequency thermionic Oscillations in the valve and means for applying between two electrodes of the valve a supplementary high-frequency alternating voltage, said last mentioned means including two oscillating circuits coupled together, one oscillating circuit being connected between the braking electrode and filament and the other oscillating circuit between the grid and the filament of the valve.

'7. An arrangement for generating ultra-short electrical waves modulated at a high frequency, comprising a thermionic valve having a filament and consisting of a grid electrode of high positive voltage of several hundred volts and a braking electrode of a lower voltage of only a few volts in relation to the filament, producing ultrahigh-frequency thermionic oscillations in the valve and means for applying between two electrodes of the valve a supplementary high-frequency 'alternatng voltage, said last mentioned means including a high frequency parallel tuned oscillating circuit connected between two electrodes of the thermionic valve, and a coil coupled to said oscillatory circuit, adapted to transmit the electrical oscillations of the mentioned circuit to a second utilization circuit.

ERNST GERHARD. 

